In high frequency applications, the small wavelength of transmitted electromagnetic radiation enables the use of relatively smaller antennas. Within this size niche is the need for antennas having broad band capability. A satellite having a large number of channels operating on different frequencies, for example, would have the need for a compact multi-band antenna. Even though higher frequency antennas are generally smaller, the size and weight limitations on spacecraft would still require the smallest of the smaller antennas.
As frequencies of use in all types of service approach higher and higher levels, the compact size of the transmitting/receiving array enables an ever increasing number of uses. In the oil reservoir exploration field, the ability to electromagnetically characterize the surrounding strata, especially with a wide band of frequencies, would be especially advantageous. The size and bandwidth of the antenna directly relate to such usefulness since both the transmitting and receiving array must be able to fit in the borehole.
In spread spectrum service, an antenna with a wide band wavelength characteristic would eliminate the need for simultaneous use of several different antennas.
For example, U.S. Pat. No. 3,110,030 to Cole, Jr, entitled "Cone Mounted Logarithmic Dipole Array Antenna" discloses antenna united for use on an aerodynamic vehicle.
U.S. Pat. No. 3,286,268 to Barbano, entitled "Log Periodic Antenna With Parasitic Elements Interspersed In Log Periodic Manner" discloses improved log periodic dipole and monopole antenna arrays and broadband antennas.
U.S. Pat. No. 3,308,470 to Bell, entitled "Tapered Ladder Log Periodic Antenna" discloses a symmetrical antenna of the log-periodic type.
U.S. Pat. No. 3,369,243 to Greiser, entitled "Log-Periodic Antenna Structure" discloses a wide band folded element type antenna structure having a plurality of series fed folded elements varying in length and spacing, and a series of phasing elements allowing control of the phase progression of the element currents.
U.S. Pat. No. 3,101,474 to Wickersham, Jr. et al., entitled "Log Periodic Type Antenna Mounted On Ground Plane And Fed By Tapered Feed" discloses a broadband "tapered" array utilizing radiating elements whose lengths are functions of element position in the array.
U.S. Pat. No. 3,500,424 to Barbano et al., entitled "Furlable Antenna" discloses planar conductive patterns comprising dipole radiating elements and feed lines of the antenna formed by printed circuit techniques on the same side of a flexible nylon sheet.
U.S. Pat. No. 3,543,277 to Pullara, entitled "Reduced Size Broadband Antenna" discloses an improved reduced size log periodic antenna in which selected elements are successively loaded to reduce the resonant frequency of such selected elements, thus to provide a desirable overall reduction in operating frequency of the antenna as compared to the lowest operating frequency of prior art antenna of similar size, while maintaining essentially frequency-independent performance over a very wide frequency range.
U.S. Pat. No. 3,550,143 to Grant, entitled "Multiple Tooth Log-Periodic Trapezoidal Array" discloses antenna arrays for use in transmission or reception wherein a novel multiple tooth trapezoidal array having multiple tapered zones is arranged in such a manner as to obtain high impedance, low capacitive coupling, and a unidirectional radiation pattern exhibiting higher gain and broad band response as compared with conventional techniques.
U.S. Pat. No. 3,633,207 to Ingerson et al., entitled "Modulated Impedance Feeding System For Log-Periodic Antennas" discloses a broadband feed system for log-periodic antennas, including loading elements, a transmission line to couple energy to or from the elements, and impedance-modulating means for matching the image impedances of the transmission line and the loading elements in the regions of local reflections to realize essentially frequency independent performance.
U.S. Pat. No. 4,101,895 to Jones, Jr., entitled "Multifrequency Antenna System Integrated Into A Radome" discloses an antenna system that comprises two or more linear arrays within close proximity which can be integrated into a conical dielectric radome.
U.S. Pat. No. 4,594,595 to Struckman, entitled "Circular Log-Periodic Direction-Finder Array" discloses a circular frequency-independent antenna array including a plurality of radially extending log-periodic subarrays of slot radiators provided in a ground-plane conductor.
U.S. Pat. No. 4,652,889 to Bizourard et al., entitled "Plane Periodic Antenna" discloses a plane periodic antenna that comprises a conductive plate having radiating elements formed from two lines of flat teeth.
U.S. Pat. No. 4,616,233 to Westerman, entitled "Twin Zig Zag Log Periodic Antenna" discloses a log periodic antenna comprising two substantially identical nonresonant elongated log periodic conductive zig zag structures.
UK Patent Application No. 2 064 877 A to Hall, entitled "Microstrip Antenna" discloses a wide band log periodic microstrip antenna comprising a feedline having a succession of conducting sheet radiators spaced along it from the input end.
All antenna designs involve a degree of tradeoff between size and gain, but broadband antennas involve a trade off between the gain sacrificed by departing from a virtually infinite array of single frequency antennas to arrive at a single structure which will adequately receive a wide frequency band of electromagnetic radiation. While maximizing the signal power received in the wide frequency band.